move helpers to util

1 files changed, 477 insertions, 0 deletions

diff --git a/packages/taler-wallet-core/src/denominations.ts b/packages/taler-wallet-core/src/denominations.ts
new file mode 100644
index 000000000..177070622
--- /dev/null
+++ b/packages/taler-wallet-core/src/denominations.ts
@@ -0,0 +1,477 @@
+/*
+ This file is part of GNU Taler
+ (C) 2021 Taler Systems S.A.
+
+ GNU Taler is free software; you can redistribute it and/or modify it under the
+ terms of the GNU General Public License as published by the Free Software
+ Foundation; either version 3, or (at your option) any later version.
+
+ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+import {
+  AbsoluteTime,
+  AmountJson,
+  Amounts,
+  AmountString,
+  DenominationInfo,
+  Duration,
+  durationFromSpec,
+  FeeDescription,
+  FeeDescriptionPair,
+  TalerProtocolTimestamp,
+  TimePoint,
+} from "@gnu-taler/taler-util";
+import { DenominationRecord, timestampProtocolFromDb } from "./db.js";
+
+/**
+ * Given a list of denominations with the same value and same period of time:
+ * return the one that will be used.
+ * The best denomination is the one that will minimize the fee cost.
+ *
+ * @param list denominations of same value
+ * @returns
+ */
+export function selectBestForOverlappingDenominations<
+  T extends DenominationInfo,
+>(list: T[]): T | undefined {
+  let minDeposit: DenominationInfo | undefined = undefined;
+  //TODO: improve denomination selection, this is a trivial implementation
+  list.forEach((e) => {
+    if (minDeposit === undefined) {
+      minDeposit = e;
+      return;
+    }
+    if (Amounts.cmp(minDeposit.feeDeposit, e.feeDeposit) > -1) {
+      minDeposit = e;
+    }
+  });
+  return minDeposit;
+}
+
+export function selectMinimumFee<T extends { fee: AmountString }>(
+  list: T[],
+): T | undefined {
+  let minFee: T | undefined = undefined;
+  //TODO: improve denomination selection, this is a trivial implementation
+  list.forEach((e) => {
+    if (minFee === undefined) {
+      minFee = e;
+      return;
+    }
+    if (Amounts.cmp(minFee.fee, e.fee) > -1) {
+      minFee = e;
+    }
+  });
+  return minFee;
+}
+
+type PropsWithReturnType<T extends object, F> = Exclude<
+  {
+    [K in keyof T]: T[K] extends F ? K : never;
+  }[keyof T],
+  undefined
+>;
+
+/**
+ * Takes two timelines and create one to compare them.
+ *
+ * For both lists the next condition should be true:
+ * for any element in the position "idx" then
+ * list[idx].until === list[idx+1].from
+ *
+ * @see {createTimeline}
+ *
+ * @param left list denominations @type {FeeDescription}
+ * @param right list denominations @type {FeeDescription}
+ * @returns list of pairs for the same time
+ */
+export function createPairTimeline(
+  left: FeeDescription[],
+  right: FeeDescription[],
+): FeeDescriptionPair[] {
+  //FIXME: we need to create a copy of the array because
+  //this algorithm is using splice, remove splice and
+  //remove this array duplication
+  left = [...left];
+  right = [...right];
+
+  //both list empty, discarded
+  if (left.length === 0 && right.length === 0) return [];
+
+  const pairList: FeeDescriptionPair[] = [];
+
+  let li = 0; //left list index
+  let ri = 0; //right list index
+
+  while (li < left.length && ri < right.length) {
+    const currentGroup =
+      Number.parseFloat(left[li].group) < Number.parseFloat(right[ri].group)
+        ? left[li].group
+        : right[ri].group;
+    const lgs = li; //left group start index
+    const rgs = ri; //right group start index
+
+    let lgl = 0; //left group length (until next value)
+    while (li + lgl < left.length && left[li + lgl].group === currentGroup) {
+      lgl++;
+    }
+    let rgl = 0; //right group length (until next value)
+    while (ri + rgl < right.length && right[ri + rgl].group === currentGroup) {
+      rgl++;
+    }
+    const leftGroupIsEmpty = lgl === 0;
+    const rightGroupIsEmpty = rgl === 0;
+    //check which start after, add gap so both list starts at the same time
+    // one list may be empty
+    const leftStartTime: AbsoluteTime = leftGroupIsEmpty
+      ? AbsoluteTime.never()
+      : left[li].from;
+    const rightStartTime: AbsoluteTime = rightGroupIsEmpty
+      ? AbsoluteTime.never()
+      : right[ri].from;
+
+    //first time cut is the smallest time
+    let timeCut: AbsoluteTime = leftStartTime;
+
+    if (AbsoluteTime.cmp(leftStartTime, rightStartTime) < 0) {
+      const ends = rightGroupIsEmpty ? left[li + lgl - 1].until : right[0].from;
+
+      right.splice(ri, 0, {
+        from: leftStartTime,
+        until: ends,
+        group: left[li].group,
+      });
+      rgl++;
+
+      timeCut = leftStartTime;
+    }
+    if (AbsoluteTime.cmp(leftStartTime, rightStartTime) > 0) {
+      const ends = leftGroupIsEmpty ? right[ri + rgl - 1].until : left[0].from;
+
+      left.splice(li, 0, {
+        from: rightStartTime,
+        until: ends,
+        group: right[ri].group,
+      });
+      lgl++;
+
+      timeCut = rightStartTime;
+    }
+
+    //check which ends sooner, add gap so both list ends at the same time
+    // here both list are non empty
+    const leftEndTime: AbsoluteTime = left[li + lgl - 1].until;
+    const rightEndTime: AbsoluteTime = right[ri + rgl - 1].until;
+
+    if (AbsoluteTime.cmp(leftEndTime, rightEndTime) > 0) {
+      right.splice(ri + rgl, 0, {
+        from: rightEndTime,
+        until: leftEndTime,
+        group: left[0].group,
+      });
+      rgl++;
+    }
+    if (AbsoluteTime.cmp(leftEndTime, rightEndTime) < 0) {
+      left.splice(li + lgl, 0, {
+        from: leftEndTime,
+        until: rightEndTime,
+        group: right[0].group,
+      });
+      lgl++;
+    }
+
+    //now both lists are non empty and (starts,ends) at the same time
+    while (li < lgs + lgl && ri < rgs + rgl) {
+      if (
+        AbsoluteTime.cmp(left[li].from, timeCut) !== 0 &&
+        AbsoluteTime.cmp(right[ri].from, timeCut) !== 0
+      ) {
+        // timeCut comes from the latest "until" (expiration from the previous)
+        // and this value comes from the latest left or right
+        // it should be the same as the "from" from one of the latest left or right
+        // otherwise it means that there is missing a gap object in the middle
+        // the list is not complete and the behavior is undefined
+        throw Error(
+          "one of the list is not completed: list[i].until !== list[i+1].from",
+        );
+      }
+
+      pairList.push({
+        left: left[li].fee,
+        right: right[ri].fee,
+        from: timeCut,
+        until: AbsoluteTime.never(),
+        group: currentGroup,
+      });
+
+      if (left[li].until.t_ms === right[ri].until.t_ms) {
+        timeCut = left[li].until;
+        ri++;
+        li++;
+      } else if (left[li].until.t_ms < right[ri].until.t_ms) {
+        timeCut = left[li].until;
+        li++;
+      } else if (left[li].until.t_ms > right[ri].until.t_ms) {
+        timeCut = right[ri].until;
+        ri++;
+      }
+      pairList[pairList.length - 1].until = timeCut;
+
+      // if (
+      //   (li < left.length && left[li].group !== currentGroup) ||
+      //   (ri < right.length && right[ri].group !== currentGroup)
+      // ) {
+      //   //value changed, should break
+      //   //this if will catch when both (left and right) change at the same time
+      //   //if just one side changed it will catch in the while condition
+      //   break;
+      // }
+    }
+  }
+  //one of the list left or right can still have elements
+  if (li < left.length) {
+    let timeCut =
+      pairList.length > 0 &&
+      pairList[pairList.length - 1].group === left[li].group
+        ? pairList[pairList.length - 1].until
+        : left[li].from;
+    while (li < left.length) {
+      pairList.push({
+        left: left[li].fee,
+        right: undefined,
+        from: timeCut,
+        until: left[li].until,
+        group: left[li].group,
+      });
+      timeCut = left[li].until;
+      li++;
+    }
+  }
+  if (ri < right.length) {
+    let timeCut =
+      pairList.length > 0 &&
+      pairList[pairList.length - 1].group === right[ri].group
+        ? pairList[pairList.length - 1].until
+        : right[ri].from;
+    while (ri < right.length) {
+      pairList.push({
+        right: right[ri].fee,
+        left: undefined,
+        from: timeCut,
+        until: right[ri].until,
+        group: right[ri].group,
+      });
+      timeCut = right[ri].until;
+      ri++;
+    }
+  }
+  return pairList;
+}
+
+/**
+ * Create a usage timeline with the entity given.
+ *
+ * If there are multiple entities that can be used in the same period,
+ * the list will contain the one that minimize the fee cost.
+ * @see selectBestForOverlappingDenominations
+ *
+ * @param list list of entities
+ * @param idProp property used for identification
+ * @param periodStartProp property of element of the list that will be used as start of the usage period
+ * @param periodEndProp property of element of the list that will be used as end of the usage period
+ * @param feeProp property of the element of the list that will be used as fee reference
+ * @param groupProp property of the element of the list that will be used for grouping
+ * @returns  list of @type {FeeDescription} sorted by usage period
+ */
+export function createTimeline<Type extends object>(
+  list: Type[],
+  idProp: PropsWithReturnType<Type, string>,
+  periodStartProp: PropsWithReturnType<Type, TalerProtocolTimestamp>,
+  periodEndProp: PropsWithReturnType<Type, TalerProtocolTimestamp>,
+  feeProp: PropsWithReturnType<Type, AmountString>,
+  groupProp: PropsWithReturnType<Type, string> | undefined,
+  selectBestForOverlapping: (l: Type[]) => Type | undefined,
+): FeeDescription[] {
+  /**
+   * First we create a list with with point in the timeline sorted
+   * by time and categorized by starting or ending.
+   */
+  const sortedPointsInTime = list
+    .reduce((ps, denom) => {
+      //exclude denoms with bad configuration
+      const id = denom[idProp] as string;
+      const stampStart = denom[periodStartProp] as TalerProtocolTimestamp;
+      const stampEnd = denom[periodEndProp] as TalerProtocolTimestamp;
+      const fee = denom[feeProp] as AmountJson;
+      const group = !groupProp ? "" : (denom[groupProp] as string);
+
+      if (!id) {
+        throw Error(
+          `denomination without hash ${JSON.stringify(denom, undefined, 2)}`,
+        );
+      }
+      if (stampStart.t_s >= stampEnd.t_s) {
+        throw Error(`denom ${id} has start after the end`);
+      }
+      ps.push({
+        type: "start",
+        fee: Amounts.stringify(fee),
+        group,
+        id,
+        moment: AbsoluteTime.fromProtocolTimestamp(stampStart),
+        denom,
+      });
+      ps.push({
+        type: "end",
+        fee: Amounts.stringify(fee),
+        group,
+        id,
+        moment: AbsoluteTime.fromProtocolTimestamp(stampEnd),
+        denom,
+      });
+      return ps;
+    }, [] as TimePoint<Type>[])
+    .sort((a, b) => {
+      const v = a.group == b.group ? 0 : a.group > b.group ? 1 : -1;
+      if (v != 0) return v;
+      const t = AbsoluteTime.cmp(a.moment, b.moment);
+      if (t != 0) return t;
+      if (a.type === b.type) return 0;
+      return a.type === "start" ? 1 : -1;
+    });
+
+  const activeAtTheSameTime: Type[] = [];
+  return sortedPointsInTime.reduce((result, cursor, idx) => {
+    /**
+     * Now that we have move one step forward, we should
+     * update the previous element ending period with the
+     * current start time.
+     */
+    let prev = result.length > 0 ? result[result.length - 1] : undefined;
+    const prevHasSameValue = prev && prev.group == cursor.group;
+    if (prev) {
+      if (prevHasSameValue) {
+        prev.until = cursor.moment;
+
+        if (prev.from.t_ms === prev.until.t_ms) {
+          result.pop();
+          prev = result[result.length - 1];
+        }
+      } else {
+        // the last end adds a gap that we have to remove
+        result.pop();
+      }
+    }
+
+    /**
+     * With the current moment in the iteration we
+     * should keep updated which entities are current
+     * active in this period of time.
+     */
+    if (cursor.type === "end") {
+      const loc = activeAtTheSameTime.findIndex((v) => v[idProp] === cursor.id);
+      if (loc === -1) {
+        throw Error(`denomination ${cursor.id} has an end but no start`);
+      }
+      activeAtTheSameTime.splice(loc, 1);
+    } else if (cursor.type === "start") {
+      activeAtTheSameTime.push(cursor.denom);
+    } else {
+      const exhaustiveCheck: never = cursor.type;
+      throw new Error(`not TimePoint defined for type: ${exhaustiveCheck}`);
+    }
+
+    if (idx == sortedPointsInTime.length - 1) {
+      /**
+       * This is the last element in the list, if we continue
+       * a gap will normally be added which is not necessary.
+       * Also, the last element should be ending and the list of active
+       * element should be empty
+       */
+      if (cursor.type !== "end") {
+        throw Error(
+          `denomination ${cursor.id} starts after ending or doesn't have an ending`,
+        );
+      }
+      if (activeAtTheSameTime.length > 0) {
+        throw Error(
+          `there are ${activeAtTheSameTime.length} denominations without ending`,
+        );
+      }
+      return result;
+    }
+
+    const current = selectBestForOverlapping(activeAtTheSameTime);
+
+    if (current) {
+      /**
+       * We have a candidate to add in the list, check that we are
+       * not adding a duplicate.
+       * Next element in the list will defined the ending.
+       */
+      const currentFee = current[feeProp] as AmountJson;
+      if (
+        prev === undefined || //is the first
+        !prev.fee || //is a gap
+        Amounts.cmp(prev.fee, currentFee) !== 0 // prev has different fee
+      ) {
+        result.push({
+          group: cursor.group,
+          from: cursor.moment,
+          until: AbsoluteTime.never(), //not yet known
+          fee: Amounts.stringify(currentFee),
+        });
+      } else {
+        prev.until = cursor.moment;
+      }
+    } else {
+      /**
+       * No active element in this period of time, so we add a gap (no fee)
+       * Next element in the list will defined the ending.
+       */
+      result.push({
+        group: cursor.group,
+        from: cursor.moment,
+        until: AbsoluteTime.never(), //not yet known
+      });
+    }
+
+    return result;
+  }, [] as FeeDescription[]);
+}
+
+/**
+ * Check if a denom is withdrawable based on the expiration time,
+ * revocation and offered state.
+ */
+export function isWithdrawableDenom(
+  d: DenominationRecord,
+  denomselAllowLate?: boolean,
+): boolean {
+  const now = AbsoluteTime.now();
+  const start = AbsoluteTime.fromProtocolTimestamp(
+    timestampProtocolFromDb(d.stampStart),
+  );
+  const withdrawExpire = AbsoluteTime.fromProtocolTimestamp(
+    timestampProtocolFromDb(d.stampExpireWithdraw),
+  );
+  const started = AbsoluteTime.cmp(now, start) >= 0;
+  let lastPossibleWithdraw: AbsoluteTime;
+  if (denomselAllowLate) {
+    lastPossibleWithdraw = start;
+  } else {
+    lastPossibleWithdraw = AbsoluteTime.subtractDuraction(
+      withdrawExpire,
+      durationFromSpec({ minutes: 5 }),
+    );
+  }
+  const remaining = Duration.getRemaining(lastPossibleWithdraw, now);
+  const stillOkay = remaining.d_ms !== 0;
+  return started && stillOkay && !d.isRevoked && d.isOffered;
+}